Cellular wireless communications systems, methods and radioterminals are widely used for voice and/or data communications. As is well known to those having skill in the art, cellular wireless communications systems, methods and radioterminals include terrestrial cellular wireless communications systems, methods and radioterminals, and/or satellite cellular wireless communications systems, methods and mobile terminals. As used herein, the term “radioterminal” includes cellular and/or satellite radiotelephones with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radiotelephone with data processing, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and/or a pager, Internet/Intranet access, Web browser, organizer and/or calendar; and/or conventional laptop and/or palmtop computers or other appliances, which include a radio frequency transceiver. A radioterminal also may be referred to herein as a “wireless terminal” or simply as a “terminal”. As used herein, the term(s) “radioterminal”, “wireless terminal” and/or “terminal” also include(s) any other radiating user device/equipment/source that may have time-varying or fixed geographic coordinates and/or may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based) and/or situated and/or configured to operate locally and/or in a distributed fashion over one or more terrestrial and/or extra-terrestrial location(s).
It may be desirable, and may be mandatory in the future, that radioterminals be equipped to determine the geographical location thereof, for example, to support emergency position reporting, often referred to as “E911” position reporting. One way to accomplish this result is to add a GPS receiver to a radioterminal. As is well known to those having skill in the art, GPS is a satellite navigation system that is funded by and controlled by the U.S. Department of Defense, that provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and/or time. As used herein, the term “GPS” also includes other satellite-based systems that can be used to measure positions on the earth, such as GLONASS.
GPS receivers may be expensive, increase radioterminal size and/or consume the limited amount of battery power that is available to the radioterminal. Accordingly, techniques have been proposed to integrate some or all of a GPS receiver into a radioterminal. See, for example, U.S. Pat. No. 6,424,826 to Horton et al., entitled Systems and Methods for Sharing Reference Frequency Signals Within a Wireless Mobile Terminal Between a Wireless Transceiver and a Global Positioning System Receiver; U.S. Pat. No. 6,097,974 to Camp, Jr. et al., entitled Combined GPS and Wide Bandwidth Radiotelephone Terminals and Methods; and U.S. Pat. No. 6,041,222 to Horton et al., entitled Systems and Methods for Sharing Reference Frequency Signals Within a Wireless Mobile Terminal Between a Wireless Transceiver and a Global Positioning System.
It is also known to add a GPS mode filter to a combined radioterminal/GPS terminal, as described in U.S. Pat. No. 6,785,543 to coinventor Karabinis, entitled Filters for Combined Radiotelephone/GPS Terminals, assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein.